Mobile data traffic has grown dramatically over the past several years and is continuing to grow rapidly due to the explosive increase of data-hungry services, as well as always connected smart mobile devices. In order to meet the capacity challenges, heterogeneous networks consisting of macro cells and small cells are considered as a promising solution. With different carrier frequencies deployed at macro cell and small cell layers, dual connectivity can be provided so as to allow a user equipment to simultaneously receive data from both a macro cell base station and a small cell base station.
Directional transmission based on antenna array beamforming in the millimeter wave band have been considered as an ideal candidate for the short range communications to be delivered by the small cells of heterogeneous networks. However, a main issue in millimeter wave communications is known as ‘deafness’ which occurs when the main beams of a transmitter and the intended receiver are not aligned and which deteriorate the communication performance.
To address this issue, a conventional beam-searching procedure is used prior to the establishment of the millimeter wave communication link. However, conventional beam-searching procedure requires performing an exhaustive search over all possible combinations of transmission and reception directions through a sequence of pilot transmissions.
Unsurprisingly, conventional beam-searching procedure requires a lot of time and power in order to find the best beam sets since the search time depends on the number of directions that have to be searched. Hence, an efficient beam-searching procedure is needed.